Paul Walker stars as an undercover detective in a futuristic city in 'Brick Mansions.' / Philippe Bosse, Relativity Media

by Bryan Alexander, USA TODAY

by Bryan Alexander, USA TODAY

In November 2013, Paul Walker was first able to see a working version of his highly physical role in Brick Mansions.

To put it mildly, Walker was stoked for the action film.

"He was like a little kid, that kind of excited," says French director Camille Delamarre, who saw Walker in the sound studio. "Like a kid when they are proud of what they had just done. That's how Paul was after he had seen his role in this movie."

Four days after leaving the studio, Walker, 40, was killed when his financial adviser and friend Roger Rodas crashed a Porsche Carrera GT into a tree after a charity event the two attended.

The tragic death was devastating to family and friends of the laid-back, Southern California-born star, whose easy charm had made him the focal point of the highly popular Fast & Furious film franchise. The seventh installment had been on shooting hiatus when the accident occurred.

It also came as Walker was starting to branch out as an actor. Brick Mansions (out April 25) demanded a new level of physicality for his role alongside David Belle, the founder of the international Parkour movement, developed from military obstacle-course training.

Brick Mansions is the American adaption of District B-13 and District B-13 Ultimatum, worldwide Parkour hits starring Belle. Walker was introduced to both of these films by his nephew and became an instant fan of Belle and the acrobatic urban discipline.

"Watching David run around doing all that crazy stuff on rooftops, breaking through windows and flips like those rodeo guys - he was incredible," Walker said in post-filming interview excerpts obtained by USA TODAY. "After that, we spent about two hours on YouTube watching Parkour."

Walker jumped at the chance to work alongside Belle. "I was like, 'Oh, cool, I get to go play, and I get to face some physical challenges, have some fun and jump off rooftops," he said.

Belle, 40, came out of action-film retirement to star as a convict in Brick Mansions, helping Walker's undercover detective bring down a crime kingpin (played by the rapper RZA) in a futuristic, walled-in city.

Walker practiced Parkour extensively with a full-time personal trainer. He even hired the film's jiu-jitsu instructor, Ricardo Miller, to travel with him on a trip to Canada to ensure uninterrupted work. The athletic beginner quickly took to both disciplines.

"(Walker) told me that his goal in the future was to be recognized not only for the movies with the fast cars, but also as the guy that introduced Parkour, Brazilian jiu jitsu moves to Hollywood," Miller says. "Unfortunately, he did not have enough time to do it all."

Frenchman Belle, in his first English-speaking part, says he met his spiritual soul mate in Walker. "He was a little crazy, like me," Belle says. "His friends used to call him Peter Pan because he had the spirit of a child. When we met, (Walker) said to me, 'I think I found someone with a more youthful spirit than myself.' "

On the rigorous Montreal set, Belle says he and Walker shared the same chiropractor after shooting their stunt-filled scenes.

"We got hurt all the time," he says. "Our trailers were side-by-side. The chiropractor would work on one of us and then just walk over to the other trailer. One injury would disappear, and another would appear somewhere else."

Walker was serious about the work. But Belle says he never lost his Peter Pan wonder.

"The set was like a playground for Paul," Belle says. "Sometimes, he would make me laugh just before a take when I was all serious and focused. I would have to get my wits together. There was always joy and fun with him."

After a four-month halt following Walker's tragic death, production has just resumed for Fast & Furious 7. But it's still unclear how Walker's unfinished role as Brian O'Connor will work into the revamped production.

"It was a big triumph for Paul - he had never done a movie like this," Delamarre says. "He pushed himself so hard here, and the results are better than we could have ever hoped for. They are incredible."